How babies learn language: Unraveling the mystery

From birth to age 7, children are geniuses at learning language. After that, the ability starts dropping dramatically before leveling out at 17 or 18. How babies learn language – what goes on in their brains – is a mystery still being unraveled.

The next decade should bring an explosion of new knowledge about how babies learn language, according to Dr. Patricia Kuhl, a groundbreaking researcher in early language and bilingual development. Her work has played a major role in demonstrating how early exposure to language alters the brain.

Dr. Kuhl spoke Aug. 23 at the University of Alaska Anchorage, on “How infants crack the speech code: Exploring minds in the making using the tools of modern neuroscience” – Available on podcast.

Baby brains are very sensitive to subtle sound differences and they register how often they hear particular sounds. At 6 months, babies distinguish the minuscule variations in sounds that mark different languages. And they can do so for every language in the world.

A critical period in language development occurs between 8 months and 10 months, when babies begin to focus on the sounds of a particular language and lose the ability to hear subtle sounds of other languages. That’s when Japanese babies lose the ability to hear the difference between “ra” and “la,” sounds not used in the Japanese language.

Dr. Kuhl described one experiment that demonstrated babies’ abilities to easily absorb a second language as well as the essential role of social interaction. American babies were exposed to a Mandarin-speaking adult in regular sessions over the course of six weeks. Tested afterward, the American babies were able to distinguish the sounds of Mandarin as well as their Taiwanese counterparts.

The experiment was repeated using audio and video of the same Mandarin-language sessions. The babies appeared to be involved and interested, but they were not able to differentiate the Mandarin sounds.

Experiment after experiment demonstrates that social interaction is essential to learning. “The more social the baby, the more learning there is. The degree of social interaction is a predictor of learning,” Dr. Kuhl said.

Every language and culture in the world uses baby talk, or “motherese,” Dr. Kuhl said. Motherese isn’t nonsense. It uses real words, with long pauses and higher pitch.

“Babies seek motherese. We think it’s brain food for them,” she said. Research into motherese also seems to shed some light on autism. Unlike normal babies, those with autism prefer non-speech sounds over motherese.

Dr. Kuhl said more understanding about babies’ brains will emerge thanks to a new brain imaging tool, the MEG, which can be used with babies. Unlike an MRI, the MEG is quiet, doesn’t require absolute stillness, and fits like an over-sized hairdryer hood instead of a claustrophobic tunnel.